Why do some bats use echolocation, given that they have other senses?

A very complex system of echolocation has independently evolved twice in vertebrates (michrobats and odontocetes). Also simpler models of it have appeared four times more in shrews, Rousettus (a genus of megachiropteran bats), and two species of cave dwelling birds commonly known as swiftlets. As a side note, I like to remark that all these animals are vertebrates, which talks about the incredibly capacity of variation of this group.

So many instances of aparition of echolocation are a good hint of the utility  this feature. What do have all these animals in common is that they are active hunters that need to find fast moving preys in very obscure enviroments, independently of wether these echolocators can have daylight activity or not.
 
Echolocation is mainly used to chase in late evening, night, when vision is not useful for it. It is also very efficient when you move in a mess, for example when a striking number of bats come out form a dark cavern in the evening, as is the case of Bats Caves of Texas. Sumarising, michrobats use echolocation to navigate and obtain food.
On the other hand, michrobats use vision to detect changes of light and conssequently knowing when they have to get out hunting and for long distance navigation. It is very interesting that some species of bats migrate, and also that many animals can hunt under day light in zones where the pression of predators is not very strong. Michrobats have cones cells in their eyes, which are used for daylight vision. So, vision and echolocation coexist and don't have the same paper in the animal senses, they are not redundant.

Furthermore, echolocation evolution could be also shaped by sexual selection. Let me address this matter.
Although the matter is not clear so far, it seems very probable that bats evolved echolocation once, and before they could fly. Later studies point in this direction. "The evolution of echolocation in bats", Page on sciencedirect.com, a study based on  molecular phylogenies points that   "Echolocation might have subsequently been lost in Old World fruit bats, only to evolve secondarily (by tongue clicking) in [Roussete bats]". Also another study about the ontogeny of cochlea and flight abilities, (http://onlinelibrary.wiley.com/d...  states that "These data further corroborate and support the hypothesis that  adaptations for sonar and echolocation evolved before flight in mammals."
Another one (Female Mate Choice Can Drive the Evolution of High Frequency) has used a model for demonstrating that there is a sexual predilection in females of Rhinolophus mehelyi for "preferentially select males with high frequency calls during the  mating season; high frequency males sire more off-spring, providing  evidence that echolocation calls may play a role in female mate". Under this light, it is clear that echolocation could have evolved once in bats, being secondarily lost in megachiropterans and then re-evolved in a simpler form in Rousettus. Nature is amazingly spendthrift.

_
As a totally side note, I will tell that I find intriguing how many questions asking about the reasons or causes of the evolution of a general feature in a organism or the organism itself are dismissed saying that evolution has not agenda; while when the question is about the utility of certain character or organ, the answers point to natural selection and explain the more intricate utilities of such features.
I think it is a great contradiction stressing the absence of purpose in evolution while trying to find all kind of strange reasons for every character in a living organism to be selected and preserved. Nature is devastatingly complicated and old for our brains that are not more than the result of evolution themselves.

We can neither aspire to understand it to its whole degree nor explain it as if evolution were a crime scenario and we sholud look for the crimimals.
But we can admit that some forms of evolution are quite more probable than others (and hence it is more probable to predict them) due to ecological, accidental and sexual circumstances, and also remember that not every feature/character/chracteristique in an organism is playing an positive or active role in the natural selection of the organism and that (as the very Darwinian theory of evolution states) ramdomnes has a role in evolution.
This is not the case in echolocation, which is clearly an andvantage. 

References:
Bats Are Not Blind
Page on wiley.com
Female Mate Choice Can Drive the Evolution of High Frequency Echolocation in Bats: A Case Study with  Rhinolophus mehelyi
Animal echolocation
Page on sciencedirect.com  

Are there any social, patrilineal mammals where breeding age females are forced to leave the family group?

There are many matrilineal mammal groups from lions to orcas to chimpanzees (I think).  Are there any cases where the males stay with the family group as they mature and females that enter breeding age are forced out, or does the nature of mammalian child rearing make this highly unlikely due to the need to nurse?

The answer:

Royals and old moneyrs come to my mind. And stay in for good reasons. Humans in general have very ancient formula of female juvenile dispersal, and the most clear examples in western history and society are found in these types of families.

Because we are talking about sex biased juvenile dispersal.

- Apart from humans, the animal that seems to fit better in your description is painted wolf (Lycaon pyctus). And I refer to them with a bit of surprise, I used to think that they are the canine mirror of hyenas, but this is wrong when it comes to sex ratios in packsis as biased as 3 males for every female, and males consistently remain in their natal pack while females disperse.  It is very significative the fact that reproductive females are terrificly prolific, with an average of 10 puppies by litter.

 

- Many primates, like chimpanzees, gorillas and red colubuses. Yes, chimpanzes practise female dispersal. It is bonobos the species that opts for male dispersal. This doesn't mean that male dispersal is absent, but that female dispersal is the general rule. (Humans have been mentioned before).

- Although sex biased dispersal can be linked to social and philopatric mammals, there some other factors that can favour it, such as mortality costs of it and enviromental pressures.

Some lesser known examples, in which the sex ratio at dispersal is biased towards females: procyonidae (potus flavus), chiropetra (Saccopteryx bilineata) and Equidae (horses).

Although it is not required by your question it is interesting to tell that there can also be some type of bias in sex ratio at birth in mammals, that generally are an answer to ecological selective pressures. You can find interesting this question:
In what species of mammals males tend to outnumber females?. What could be the ecological reasons?

Interesting data in:
http://onlinelibrary.wiley.com/d...

 

Cuando una tercera especie ayuda a dos especies de pájaros insectívoros. O cómo lograr que una pregunta sobre etología parezca un problema de álgebra.

En Quora se puede preguntar casi por cualquier cosa, por eso mola, pero no de cualquier manera. Primero tienes que plantear la pregunta, en inglés, y después intentar explicarla como mejor se te ocurra, en ingés también. Y resulta que en eso de explicar las cosas hay gente que tiene especial gracia, o al menos a mi me lo parece.

Esta es de una que pregunta por una relación entre distintas especies de aves insectívoras y un tercer agente que les facilita encontrarse la comida. Y cuál es el chiste, pues que es capaz de contar esto haciendo que parezca una ecuación de tercer grado:

La pregunta:

Which animal/bird/insect best describes such situation?

- X is looking for Y.
- Z is also looking for Y.

And
- W makes Y available to both X and Z.

I am looking for a name of animal/bird/insect who are facing such situation in their food chain. It would be great if someone provide names of W,X,Y and Z.

 

O sea:

 

[¿Qué animal/ave/insecto describe mejor esta situación?

 

- X está buscando Y.

- Z está buscando Y, también.

 

Y

- W hace que Y esté disponible para X y Z, los dos a la vez.

 

Estoy buscando un nombre para un animal/ave/insecto que se enfrenten a esa situación en su cadena alimentaria. Sería estupendo si alguien proporciona los nombres de W, X, Y y Z. ]

Consideraciones:

 

1) Quien ha hecho esta pregunta tiene mérito. Los escritores de libros de texto tendrían un filón con él. Imagínate cómo plantearía el muchacho el típico problema de "un tren sale de la estación A a una velocidad de...". 

2) Esto de llamar animales sólo a los mamíferos es una cosa muy extendida en inglés. En el contexto de la pregunta recordar "animales = mamíferos".

3) Esta es la típica pregunta que riza el rizo. No le interesa un insectívoro, sino que quiere dos distintos.

4) Vuélvete a leer la pregunta que no te has enterado de nada.

 

Después de releer la pregunta al menos 3 veces...

 

 

La respuesta:

 

Funny question, it sounds like and algebra problem :). I like it.

[Note: I will answer expecting that your question isn't a homework, because as I have told I find it very interesting. But in case it is, I wouldn't show your teacher these rambling divagations I'm going to write here, teachers frequently expect that the answers are centered on their local area, so...good luck if you use this material...].
[Note 2: I think that in marine habitats this type of situation is more frequent given that there are many more intermediate predators than in terrestrial habitats].

Such as you have posed it, I don't remember any direct example of two different insectivore birds looking for the same kind of insect, and an aditional element (W, you don't specify wether W is a bird, or even an animal) making those insects avalaible to their predators.

But I can tell of some similar situations:

1) W accidentally or as the collateral result of its activities makes some preys accessible to some predators. There are a bunch of situations of this kind occurring in many ecosystems everyday, to tell you about some:

• W is a maize farmer who uses flood irrigation methods. Y are some different types of flies (Diptera) that lay their eggs in the flooded fields of W. As a result massive quantities of adult flying insects are avalaible for many insectivore birds, migratory ornot, such as sparrows, swifts, swallows, bee-eaters, etc, etc. They are yor X and Z (and the rest of the alphabet, and more :)).  
• W is a bird that accidentally disperses invertebrates out of their habitats, burrows or even hosts. Thus these inertebrates are made available for some predators that live/chase well far from those habitats and biotopes, and that in other case wouldn't have very few chances of preying on them.
  To give them name, W could be piscivorous birds, Y propagulates, and X pelicans.

 

 

 

To give them name, W could be piscivorous birds, Y propagulates, and X pelicans.

There is a very interesting paper about the importance of birds as invertebrates dispersers in arid Australia: Page on ebd.csic.es.

2) W voluntarily tells X and Z the location of Y in order to get access to Y or some products of Y.

Honeyguides are named for a remarkable habit seen in one or two species: they guide humans to bee colonies.  Once the hive is open and the honey is taken, the bird feeds on the  remaining wax and larvae. This behavior is well studied in the greater honeyguide; some authorities (following Friedmann, 1955) state that it also occurs in the scaly-throated honeyguide, while others disagree (Short and Horne, 2002). Despite popular belief, there is no evidence that honeyguides guide the honey badger.

I give it up to you to name X, Y, Z, W in those cases.

Masturbarse es cosa de animales

Me preguntan muchas cosas en Quora últimamente. Esto me da vidilla, porque puedo saber qué le interesa a la gente, y además conocer, en ocasiones, las reacciones a las repuestas. Y es que hacer un blog es algo más solitario y para mantenerlo al día hay que querese mucho.
Hablando de solitarios y quererse, una de las preguntas más garbosas (considerando lo difícil que es tener gracia en inglés) que me han hecho es ésta:

 La pregunta: 

What are the animal species that masturbate just like humans do?

Is it some mammals, or some of the ape family? Or are there some fishes or reptiles that pleasure themselves too?
The point of interest is the method of masturbation. It need not be physically stimulating with the use of limbs, can be some thing else that the common man is unaware of.

O sea:

¿Cuáles son las especies animales que se masturban justo como hacen los humanos?.
[¿Son algunos mamíferos, o alguno de la familia de los primates?. O ¿también hay peces o reptiles que se dan placer a ellos mismos?. El asunto de interés es el método de masturbación. No tiene por qué ser estimularse físicamente con las patas, puede ser algo más que el hombre común desconozca.]

Consideraciones previas
 
Responder a este tipo de preguntas tiene su riesgo, y es que quien la hace se ha puesto en modo anónimo. Se trata de alguien que de verdad está interesado en la historia natural de la masturbación, o es un listillo que quiere descubrir nuevas experiencias... Lo que está claro es que esta pregunta sólo la redacta así un tío.

La respuesta: 

Como hacen los humanos...igual, lo que se dice igual no siempre puede ser, eso lo sabe hasta el T. rex de los chistes:

(Si Dios no quería que nos masturbáramos, nos habría hecho los brazos más cortos. Quizás por eso el T. rex estaba siempre tan enfadado).

Una pregunta graciosa, no sé si me respuesta estará a la altura de todas las risas que me ha dado la línea sobre la forma en la que lo hacen los humanos.

 

Los animales se masturban de lo lindo. Si los buscas, encontrarás un montón de vídeos de gatos, perros, caballos, cabras y cerdos lamiéndose, frotándose y resarciéndose, que están en plena sesión de masturbación. 

Las bonobas cumplen todas las premisas de las pregunta, y las redondean rotundamente

•  El auto erotismo es muy común en caballos y yeguas. Las yeguas se frotan contra postes y otros objetos, y se ha descrito que eyaculan un mucus cuando llegan al clímax.
• Las aves tienen una apertura llamada cloaca, que comparte las funciones sexual y excretoras. Los machos se masturban doblando las colas alrededor de un objeto (como un juguete, rama o incluso una mano humana) y frotando la cloaca contra éste. Pero las auténticas contorsionistas son las hembras, que elevan la cola hacia un lado y se restregan contra su objeto favorito para estas tareas.
• Las morsas demuestran una inesperada flexibilidad a la hora de estimularse con las aletas y la boca. Lo que tiene su mérito en el caso de los machos, con esos enormes colmillos.
• Las tortugas macho son muy conocidas en youtube no sólo por la habilidad con que frotan sus penes contra juguetes y rocas, sino por los gritos de placer con los que amenizan esta actividad. Ahora, en cuanto a la estimulación bucal, tienen todo que envidiarle a las morsas. Ay, esos caparazones...
• Las hembras de puercoespín en cautividad muestran un enorme interés por estructuras como platos, bebederos, troncos, etc, en época de celo. Su afán masturbatorio es especialmente creativo y se las describe sentándose a horcajadas y montando el objeto de su interés.
• Y, cómo no, los primates son excepcionalmente activos en sus actividades masturbatorias. Muchas de ellas totalmente idénticas a las de los humanos (auqnue no puede ser de otra forma, los humanos somos primates).
     

 Ahora bien, se sabe mucho más de la masturbación en mamíferos y concretamente en mamíferos machos que son las divas de la observación del comportamiento animal (y que no se engañe nadie, tanto la observación como el análisis del comportamiento animal está dominado por premisas y actitudes machistas).

¿Qué podemos saber de algunas hembras que no sean mamíferas?. En realidad hay muy pocas descripciones. Aparte de la forma de masturbarse de algunas aves, hembra, se sabe que muchas reptiles, hembra, también tienen clítoris. Por ejemplo, esta es la foto del clítoris de una cocodrila:

http://crocodilian.com/crocfaq/f...

Es muy difícil pensar que la función de estos clítoris sea otra que la de dar placer. Y si sienten placer, muy probablemente también hayan desarrollado sus formas de masturbarse. Pero lo cierto es que no hay referencias o no la he encotrado.

Más allá de mamíferos, aves y reptiles, es decir los típicos vertebrados de fecundación interna, no se sabe mucho de este asunto, si se masturban y cómo lo hacen en caso afirmativo. Los peces que practican la fecundación interna (tiburones, por ejemplo) son unos buenos candidatos. Pero también podemos sospechar de las especies en las que se realizan ritualesde estimulación para poder liberar huevos y esperma (sospechemos de los caballitos de mar). ¿Y qué hay de los invertebrados?. ¿Alguien sabe algo?.

Referencias:

http://www.livescience.com/12944-animals-evolved-masturbate.html

http://crocodilian.com/crocfaq/f..